Heretofore, in medical fields, various medical liquid feeding devices have been developed that comprise an expandable container, and a feed duct for feeding to a patient a medical liquid discharged from one end of the expandable container.
For example, Japanese Patent Publication No. 4-36027 discloses techniques related to a medical liquid feeding device 40 which comprises a long, approximately cylinder-shaped expandable container 41, an inlet port 42 for supplying a medical liquid into the expandable container 41 therethrough, and a feed duct 43 for feeding to a patient the medical liquid discharged from one end of the expandable container, as shown in FIG. 8.
This medical liquid feeding device 40 includes an approximately cylinder-shaped stressing member 44 disposed inside the expandable container 41. The stressing member 44 has an outer diameter greater than the inner diameter of the expandable container 41, and thereby the expandable container 41 is slightly stressed in its radial direction by the stressing member 44 in the state after it is fixed to the stressing member 44.
When the medical liquid feeding device 40 is used, an appropriate medical liquid is injected or supplied into the device 40 through the inlet port 42 using a syringe or the like. The supplied medical liquid is introduced into the expandable container 41 through a check valve (not shown) attached to the stressing member 44, and stored in the expandable container 41. The medical liquid pressurized by a contractive force of the expanded expandable container 41 is then fed to a patient through a hole 46 formed in the stressing member 44 and the feed duct 43.
In this medical liquid feeding device 40 equipped with the expandable container 41, a user has no other choice but to judge a fed amount of the medical liquid from changes in shape of the expandable container 41, and it is difficult for the user to judge the timing of replacement of the medical liquid feeding device 40 or the like. For this reason, according to the technique disclosed in the Patent Publication 1, a plurality of indicator bumps 47 are provided on the stressing member 44 to indicate the state when the expandable container 41 is almost emptied so as to serve as means for determining a remaining amount of the medical liquid stored in the expandable container 41. The indicator bumps 47 are designed such that they are invisible when the expandable container is expanded, and become visible in order from one located closer to either one of opposite ends of the stressing member 44 as the expandable container 41 is gradually emptied, so as to allow a user to judge a remaining amount of the medical liquid stored in the expandable container 41.
However, the above medical liquid feeding device 40 involve the problem that a remaining amount of the medical liquid stored in the expandable container 41 cannot be quantitatively determined, because the indicator bumps 47 is capable of doing no more than indicating changes in shape of the expandable container 41.
In this type of simple medical liquid feeding device, it is inappropriate to incorporate a complicated measuring mechanism thereinto to quantitatively determine a remaining amount of the medical liquid. Furthermore, in a scene where the medical liquid is being fed to a patient, it is required to quickly quantify a remaining amount of the medical liquid stored in the expandable container.
In view of the above problems, it is therefore an object of the present invention to provide a medical liquid meter for a medical liquid feeding device, capable of quantifying a remaining amount of medical liquid quickly and accurately in a scene where the medical liquid is being fed to a patient, in a simplified and low-cost structure.